This invention relates to the field of sound producing prosthetic devices for use by laryngectomized humans.
The human larynx functions to produce a tone which is modulated or otherwise acted upon by the teeth, tongue, lips, palate to produce speech. Persons who have had laryngectomy operations, or who have other laryngeal dysfunctions, are unable to speak naturally because they cannot produce the required tones.
Many devices have been developed for enabling artificial speech. The usual practice is to generate a tone within the oral cavity which can then be shaped into speech. Most such devices are located external to the oral cavity, but a few are partially inserted therein, and at least one device is entirely located within the oral cavity. This latter device is described in a European Patent Application No. (82102411.4) entitled "Artificial Larynx", European publication Ser. No. 0-061-702, filed Mar. 23, 1982, which has a U.S. application Ser. No. 249,140 filed Mar. 30, 1981 now U.S. Pat. No. 4,473,905, to Katz et al, this patent being incorporated herein by reference. The Katz device has a tone emitting circuit, battery, and speaker embedded within a flat plate which is held within the mouth like a dental plate.
The devices which are located within the oral cavity have several advantages over externally located devices, but also have the disadvantage of interference with the articulation needed to shape the tone into the sounds which are identified as speech. The physical presence of the device may prevent the lips and tongue from assuming the positions appropriate to specific sounds or words, or the device may reflect sound waves. The result is decreased quality.
Consequently it is desired to provide an improved electrolarynx with reduced interference with articulation.